A conventional composite sensor for detecting angular velocity and acceleration is configured as shown in FIGS. 8 to 11. FIGS. 8 and 9 show an exploded perspective view and a lateral sectional view of the conventional composite sensor for detecting angular velocity and acceleration. FIG. 10 shows a perspective view of an angular velocity detecting element of the conventional composite sensor for detecting angular velocity and acceleration. FIG. 11 shows a perspective view of the conventional composite sensor for detecting angular velocity and acceleration. This composite sensor includes angular velocity detecting unit 1, acceleration detecting unit 11, circuit board 15, shield case 18, protective case 25, and protective lid 36.
Angular velocity detecting unit 1 is formed of vibrator 2, housing 3, and lid 4 as shown in FIG. 10. Vibrator 2 is a tuning fork formed by bonding two thin plates made of single-crystal quartz together. Each plate of single-crystal quartz has a crystal axis different from each other. As shown in FIG. 10, vibrator 2 includes driving electrodes 5 on the front face and rear face, and detecting electrodes 6 on the outer lateral face and an inner lateral face.
Housing 3 accommodates vibrator 2 and has an opening (not shown) at the top face. Lid 4 closes the opening provided at the top face of housing 3. As shown in FIG. 8, power-supply terminal 7, angular velocity output terminal 8, and GND terminal 9 extend from the top face to the underside of lid 4. First ends of power-supply terminal 7 and angular velocity terminal 8 are electrically connected to driving electrodes 5 in vibrator 2, respectively. A first end of angular velocity output terminal 8 is electrically connected to detecting electrodes 6 of vibrator 2.
Acceleration detecting unit 11 has an acceleration signal processing IC (not shown) built-in. In acceleration detecting unit 11, a movable electrode plate (not shown), and a fixed electrode plate (not shown) are provided therein. Acceleration detecting unit 11 has power-supply terminal 12, X-axis acceleration output terminal 13A, Y-axis acceleration output terminal 13B, and GND terminal 14 each protruding outward. First ends of those terminals are electrically connected to the movable electrode plate and the fixed electrode plate.
Angular velocity detecting unit 1 is rigidly mounted to the underside of circuit board 15, which has a large number of holes 16 through which the terminals are supposed to extend from the top face to the underside of board 15. Power-supply terminal 7, angular velocity output terminal 8, and GND terminal 9 of angular velocity detecting unit 1 extend through holes 16. Acceleration detecting unit 11 is also rigidly mounted to the underside of circuit board 15. On the top face of board 15, angular velocity signal processing IC 17 is placed and IC 17 is formed of electronic components structuring an automatic gain control (AGC) circuit (not shown). IC 17 is electrically connected with power-supply terminal 7, angular velocity output terminal 8, GND terminal 9, power-supply terminal 12, X-axis acceleration output terminal 13A, Y-axis acceleration output terminal 13B, and GND terminal 14.
Metallic shield case 18 is formed of housing section 18A and lid 18C closing opening 18B of housing section 18A. Shield case 18 accommodates circuit board 15, angular velocity detecting unit 1, and acceleration detecting unit 11. Power-supply relay terminal 19, GND relay terminal 20, angular velocity relay terminal 21, X-axis acceleration relay terminal 22, and Y-axis acceleration relay terminal extend from the inside to the outside of shield case 18. Power-supply relay terminal 19 is electrically connected to power-supply terminals 7 and 12. GND relay terminal 20 is electrically connected to GND terminals 9 and 14. Angular velocity relay terminal 21 is electrically connected to angular velocity output terminal 8. X-axis acceleration relay terminal 22 is electrically connected to X-axis acceleration output terminal 13A. Y-axis acceleration relay terminal 23 is electrically connected to Y-axis acceleration output terminal 13B.
Lid 18C has elastic protrusions 24 at vertical face 18D, and elastic protrusions 24 elastically fit lid 18C onto the outer face around opening 18B of shield case 18, so that housing section 18A and lid 18C have the same electrical potential.
Protective case 25 made of resin is cylindrical and has a bottom, and accommodates shield case 18. Connector section 26 protrudes from the lateral face of protective case 25 to the outside. Inside connector section 26, first ends of power-supply connector terminal 27, angular velocity connector terminal 28, X-axis acceleration connector terminal 29, Y-axis acceleration connector terminal 30, and GND connector terminal 31 are provided. Second ends of these terminals are buried in protective case 25. Protective lid 36 made of resin closes the opening formed on the top face of protective case 25.
As shown in FIG. 11, through-holes 32 are formed so as to extend from the bottom of protective case 25 to the outside of case 25. Second ends of power-supply connector terminal 27, angular velocity connector 28, X-axis acceleration connector 29, Y-axis acceleration connector 30, and GND connector 31 are placed inside the through-holes 32. As shown in protective case 25 in FIG. 9, the second end of X-axis acceleration relay terminal 22 runs into the hole (not shown) where X-axis acceleration connecter terminal 29 runs, and the second end is electrically joined to terminal 29 with solder 35. In a similar way, the second end of Y-axis acceleration relay terminal 23 runs into the hole (not shown) where Y-axis acceleration connecter terminal 30 runs, and the second end is electrically joined to terminal 30. The second end of power-supply relay terminal 19 runs into the hole (not shown) where power-supply connecter terminal 27 runs, and the second end is electrically joined to terminal 27. The second end of angular velocity relay terminal 21 runs into the hole (not shown) where angular velocity terminal 28 runs, and the second end is electrically joined to terminal 28. The second end of GND relay terminal 20 runs into the hole (not shown) where GND connector terminal 31 runs, and the second end is electrically joined to terminal 31. The composite sensor for detecting angular velocity and acceleration discussed above is disclosed in, e.g. Patent Literature 1.
Next, the operation of the conventional composite sensor for detecting angular velocity and acceleration discussed above is described hereinafter. First, a DC voltage supplied from the power supply (not shown) externally provided is applied to angular velocity signal processing IC 17 via power-supply terminals 27 and power-supply relay terminals 19, then is converted into an AC voltage. This AC voltage is applied to driving electrodes 5 of vibrator 2 of angular velocity detecting unit 1 via power-supply terminal 7. Driving electrodes 5 are grounded via CND connector terminal 31, GND relay terminal 20, and GND terminal 9. The foregoing electrical connections allow vibrator 2 to vibrate flexibly.
In the foregoing status, angular velocity detecting unit 1 rotates at angular velocity ω on the longitudinal center axis of vibrator 2, then Coriolis force F=2 mv×ω is generated to vibrator 2, where “m” stands for mass of the arm section of the tuning fork of vibrator 2, and “v” stands for velocity of the flexion movement. Coriolis force F generates electric charges on detecting electrodes 6, and the electric charges produce an output signal which travels to angular velocity signal processing IC 17 in circuit board 15 via angular velocity output terminal 8. Angular velocity signal processing IC 17 converts this output signal into an output voltage, which is supplied to an external computer (not shown) via angular velocity relay terminal 21 and angular velocity connector terminal 28. The computer then detects an angular velocity based on this output voltage.
A voltage of 5V is applied to the movable electrode plate (not shown) and the fixed electrode plate (not shown) of acceleration detecting unit 11 via power-supply connector terminal 27, power-supply relay terminal 19, and power-supply terminal 7. In this status, acceleration is applied onto the plane of acceleration detecting unit 11 along the horizontal direction, i.e. X-axis and Y-axis, then the movable electrode plate is moved, which changes the capacitance of a capacitor (not shown) formed between the movable electrode plate and the fixed electrode plate. Acceleration detecting unit 11 then converts this change in capacitance into an output voltage. The output voltage corresponding to the acceleration along the X-axis is supplied to the computer (not shown) via X-axis acceleration output terminal 13A, X-axis acceleration relay terminal 22, and X-axis acceleration connector terminal 29. The computer detects the acceleration along the X-axis based on this output voltage. In a similar way, the output voltage corresponding to the acceleration along the Y-axis is supplied to the computer (not shown) via Y-axis acceleration output terminal 13B, Y-axis acceleration relay terminal 23, and Y-axis acceleration connector terminal 30. The computer detects the acceleration along the Y-axis based on this output voltage. The computer then analyzes angular velocities, accelerations along the X-axis and the Y-axis applied to a vehicle body, thereby analyzing the behavior of the vehicle body.
The structure discussed above includes circuit board 15 placed inside the shield case 18, and angular velocity signal processing IC 17 mounted on the top face of circuit board 15. Acceleration detecting unit 11 including the acceleration signal processing IC (not shown) therein is mounted on the underside of circuit board 15. The composite sensor for detecting angular velocity and acceleration is thus bulky.
Patent Literature 1: Unexamined Japanese Patent Publication No. 2003-4450